My shotgun is Remington Sportsman 58, 20-ga. with standard 12-ga. steel receiver that has 0.210” tickness on top. Can I drill and tap 2-holes (all the way trough) on top of receiver to mount pickatinny base 2” long for Burris Fast-Fire sight? Will these holes weaken the receiver ?

The screws that will hold pickatiny will be 6-48 and flush on the inside of the receiver and 7/8” apart.

I use mostly 3” 1-oz shells in this shotgun at 1330fps factory loads of steel shot.